The support effect on platinum catalyst under oxidizing atmosphere: improvement in the oxidation-resistance of platinum by the electrophilic property of support materials

Abstract

The support effect on platinum catalyst for low temperature propane combustion was investigated by using a series of platinum catalysts with different acid strengths support materials and different platinum dispersions. The catalytic activity of platinum catalyst varied with both the acid strength of support materials and the platinum dispersion. On each support material, the turnover frequency increased with the decrease in platinum dispersion. This variation in the turnover frequency is attributed to the variation in the oxidation state of platinum, since it was clarified by Pt LII and LIII-edge XAFS that platinum with small dispersion is less oxidized than that with large dispersion. The turnover frequency also varied with the acid strength of support materials; the turnover frequency increased with the increase in the acid strength of support materials at the same dispersion. The Pt LII and LIII-edge XAFS investigation clearly indicated that platinum on the acidic support material is less oxidized than that on basic material. Thus, it is clearly shown that the support materials affect the catalytic activity of platinum through the control of the oxidation-resistance of platinum by its electrophilic/electrophobic property, demonstrating that the electrophilic/electrophobic property of support materials is an important factor for the design of platinum catalyst under the oxidizing atmosphere.